BCL-2 associated X protein (BAX) is a proapoptotic member of the BCL-2 protein family, which plays an essential role in triggering cell commitment to apoptosis. Depending on the physiological condition of the cell, BAX shuttles between soluble (inactive) and mitochondrial outer membrane-associated conformation(s). Upon activation by various apoptotic stimuli, BAX translocates to the mitochondrial outer membrane (MOM) and undergoes a set of conformational changes leading to protein oligomerization. Ultimately, oligomerization leads to assembly of pores through which apoptogenic factors, such as cytochrome C, are released from the mitochondrial inter- membrane space to the cytosol, thus initiating apoptosis. Despite extensive research in this field, the exact mechanism by which BAX mediates MOM permeabilization as well as the nature and structure of BAX-mediated pores remain elusive. Clarifying the structural transitions that drive BAX activation and pore formation may facilitate the development of therapeutic agents that can potentially be used to treat diseases with inadequate apoptosis, such as cancer, or excessive apoptosis such as neurodegenerative disorders. In Aim 1, we will attempt to solve the 3D structure for membrane-engaged BAX using mainly NMR among other biophysical techniques. We will also structurally characterize the BAX-mediated pore. Several reports have suggested that BAX interacts with voltage dependent anion channel 1 (VDAC-1), however the significance of this interaction is not clear. In Aim 2, we will pursue the structural characterization of the VDAC-1/BAX complex. Together these aims will help us better understand the mechanistic details of BAX-mediated apoptosis.